Safety device for gas burners



April 25, 1939. BETZ AL 2,156,235

SAFETY DEVICE FOR GAS BURNERS Original Filed Nov. 24, 1933 2 Sheets-Sheet l P 1939- P. L. BETZ ET AL 2,156,235

SAFETY DEVICE FOR GAS BURNERS Original Filed Nov. 24, 1935 2 Sheets-Sheet 2 Gama/2,012 m s Patented Apr. 25, 1939 s'rArss Artur oFFicE Karrer, Washington,

D. 0., assignors to Consolidated Gas Electric Light and Power Company of Baltimore, Baltimore, Md., a corporation of Maryland Original application November 24, 1933, Serial No. 699,590. Divided and this application October 2, 1937, Serial No. 167,068

6 Claims.

This invention relates to a safety device, and more particularly to a safety device for gas burners whereby a valve in the gas line will be closed automatically whenever a flame to which it is subjected, as a pilot flame, goes out.

In Letters Patent of Sebastian Karrer, No. 2,097,838, granted November 2, 1937, for Safety device for gas burner, a device of the type characterized has been disclosed which permits the use of a relatively small valve that can be opened wide, thereby avoiding the use of valve members with only a relatively small lift with respect to their seat and the consequent need for a relatively large valve port in order that the desired flow of gas therethrough can be maintained, which may be removed from the burner to any suitable extent and disposed either above or below as well as in the plane of the burner without interfering with its sensitivity or reliability, and which uses the principle of a thermoelectric couple and an electromagnet energized by said couple to hold the valve in open position as long as the flame to which the couple is subjected is maintained but effecting a prompt closure of the valve when the flame goes out.

It is an object of this invention to provide an improved device of the character above described in which the force available for maintaining the valve in its open position is less than the force that is ultimately available for closing the valve but in excess of' that normally tending to close the valve under normal conditions.

Another object of this invention is to provide an improved device of the type characterized wherein the valve member is so actuated that when the valve is to be closed it is positively and firmly pressed into close contact with its seat by resilient means cooperating with the stem of the valve and which therefore enables the valve to be installed so that it closes against the gas pressure as well as with the gas pressure, as may be preferred.

Another object of this invention is to improve the construction of the thermocouple and its manner of submission to the controlling flame.

Another object of this invention is to provide an improved device of the character above described which is simple in construction, inexpen- 50 sive to manufacture and certain in operation.

Other objects will appear as the description of the invention proceeds.

Theinvention is capable of receiving a variety of mechanical expressions, one of which is shown 55 on the accompanying drawings, but it is to be expressly understood that the drawings are for purposes of illustration only and are not to be construed as a definition of the limits of the invention, reference being had to the appended claims for that purpose.

Referring in detail to the drawings, wherein the same reference characters are employed to designate corresponding parts in the several figures,

Fig. 1 is an axial section through a valve mechanism embodying the present invention;

Fig. 2 is a view corresponding to Fig. 1 but showing the valve in closedposition;

Fig. 3 is a plan view of the device; and

Fig. 4 is a perspective view of the valve and its operating mechanism.

The invention can be embodied in a wide variety of constructions for use with a wide variety of devices employing gas burners, but for purposes of illustration the invention has been shown as embodied in a device for automatically closing a valve in a gas line leading to the burner of a hot water heater 1 whenever the pilot of said heater goes out. The main burner is indicated at 8 and may be of any suitable construction. Said burner is supplied with gas through pipe 9, and the gas supply line may be provided, as is more or less common, with a valve under the control of a thermostat, of any suitable construction (not shown), in order that said valve may be actuated and gas supplied to or shut oil? from said burner as required to maintain the temperature of the water between predetermined limits. Also associated with said burner 8 is a pilot I of any suitable construction and supplied with gas through pipe ll. 7

In accordance with the present invention the flow of gas to the main burner 8 is to be automatically and promptly stopped by electro-responsive control mechanism whenever the pilot flame goes out, the pipe ll leading to the pilot l0 communicating with the main gas conduit on the inlet side of and ahead of the thermostatically controlled valve. As shown, a generally T-shaped valve casing l2, of any suitable size, construction and material, and which may be a brass or aluminum casting, is mounted in the main gas line, said casing having the stem of its T formed as an outlet nipple l3 with which the pipe 9 leading to the main burner is coupled in any suitable way, as by a screw threaded coupling. The arm 14 of said T-shaped housing is suitably constructedto constitute or receive a seat for the valve member. As shown, the casing is interiorly threaded at It and receives a coupling member I5, 01 any suitable material such as brass-or aluminum, which is exteriorly threaded for engagement with the threads H5, at one end,,. and at its opposite end said coupling member 15 is threaded or otherwise suitably formed for connection with the gas inlet pipe 86. Member 15, in the form shown, has its inner end coned or otherwise suitably formed so as to form a valve seat I].

Cooperating with said valve seat H is a valve member 23 of any suitable construction and material and formed on or attached to a valve stem 2| which has a sliding fit in an aperture 22 formed in the end wall 23 that closes the end of the opposite arm of the T-shaped casing. Exteriorly of said casing valve stem 2| has slidably mounted thereon a sleeve 25, preferably rectangular in external configuration, although if preferred said sleeve may have any other suitable form. Mounted on the outer end of said valve stem is a collar 26, which may be retained thereon in any suitable way as by a pin or set screw 26', and interposed between said collar 26 and said sleeve 25 is a coil spring 21 which normally urges said sleeve inwardly with respect to said stem but which may yield as hereinafter described.

Formed on or suitably attached to the end wall 23 of said casing is a suitable support 23 for one of the pivots of a toggle mechanism next to be described. As shown, said support is in the form of a lug projecting outwardly from the wall 23 and having an aperture therethrough in alinement with the aperture 22. Pivotally attached to the sleeve 25 and to the support 23 are the two arms 23 and 35 of a toggle, arm 29 being pivoted on sleeve 25 at 38, with said pivot pin passing through an elongated slot 34 in stem 2!, arm 35 being pivoted on support 28 at 32, and the two arms being pivotally connected at 33. Said toggle arms may be formed in any suitable way. As shown, each is formed of sheet metal, such as brass stamped or otherwise suitably formed into members of U-shaped or trough-shaped cross section. Member 29 has its trough of suificient width so that the arms thereof embrace the sleeve 25, and the pivot pin 31 is passed through the sides of said trough and said sleeve as well as the slot 34 in the stem 2i. Arm 30 has its trough of sufficient width so that its sides are received within the trough of arm 25, and pivot pin 33 is passed through said overlapping sides. The trough of arm 30 is also of such width that it embraces the lug 28 and pivot pin 32 passes through the sides of the trough 30 and said lug.

Arm 29 has an extension 35 beyond the pivot 33 and suitably attached to the end thereof, as by solder, is a flat bar-shaped armature 36, preferably of high permeability. Cooperating with said toggle mechanism is suitable resilient means for normally urging the toggle arms to angular relationship, as shown in Fig. 2. Said resilient means may be provided in any suitable way, but are shown as composed of a pair of coil springs 31 connected at their opposite ends to the pivot pins 3| and 32 and retained thereon in anysuitable way. Also interposed between the extension 35 and arm 30, and here shown'as suitably attached to extension 35, is a leaf spring 42 which engages the arm 30 and is tensioned thereby. Hence spring 42 provides an initial force to move the toggle arms of! dead center when the armature is released.

tutes a support for the electromagnet. Said elec tromagnet may be of any suitable size and construction, but for simplicity it is preferably formed as follows: A U-shaped bar 39 of iron, preferably of high permeability and shown as on the order of in diameter, has. thereon the operating winding of said control mechanism, here shown as two coils 4D and 4! wound on its two legs and composed of wire of relatively low resistance, on the order of .125 in diameter, each coil being composed of a suitable number of turns, on the order of twenty. Said coils may be wrapped with any suitable insulating cover. Flange 38 is provided with a pair of apertures 43 which are spaced in conformity with the spacing of the legs of the U-shaped core of the electromagnet, and said electromagnet is supported in said flange by projecting the ends of the legs through said apertures 43, after which said legs may be secured in said apertures in any suitable way, as by set screws 44. The ends of said core are thus located below the flange 38 as viewed in the drawings, and are positioned to be engaged by the armature 35 when the parts are in the relative position shown in Fig. 1, the end faces of the core providing pole faces of relatively large area for contact with the armature.

The leads 45 and 46 from the electromagnet coils or operating winding extend toward the pilot I0 and may be bent or curved to any suitable extent. Said leads are connected to a thermoelectric couple unit generally designated 48 and which may be of any suitable construction but is shown as having two arms with an intermediate hot junction as hereinafter described. As shown, said unit is composed of a pair of conducting arms 49 and 55, which may be made of thesame material and size as the wire constituting the coils of the electromagnet provided that sufiicient rigidity of the arms is thus efi'ected, and said arms are detachably connected to the leads 45 and 46 respectively by couplings 4'! of any suitable character. Suitably attached to the ends of the arms 49 and 50 in the form illustrated are the two members 5! and 52 of the thermoelectric couple or thermo-couple having a so-called hot junction at 53 that preferably has a suitable frame resistant extension 53' of an intermediate metal which is directly subjected to the action of the flame. Said thermoelectric couple may be formed of any suitable material, such as Chromel- Constantin. The arms 49 and 50 are of such length and extend in such a direction as to dispose the junction 53 or its flame resistant extension 53' in the flame of the pilot I0. As said arms 49 and 50 and the leads 45 and 46 may be made of any suitable length, the valve casing 2 with its associated parts may be disposed at any suitable distance from the main burner 8 and pilot burner I0 so as to remove the valve casing and its associated parts from the zone of high heat around the burner. The members 5| and 52 may be of any suitable length to maintain the proper temperature difierential between the junction 53 and the opposite ends or so-called cold junctions 54 and 55 of said members in order to obtain the desired thermoelectric current, but as the material of the terminals 5| and 52 is ordinarily relatively expensive the junctions 54 and 55 are preferably made as close to the junction 53 as is consistent with the maintenance of a proper difference in temperature therebetween. As shown in Figs. 3 and 4 the thermocouple 5|, 53, 52 is preferably disposed entirely within the burner chamber or compartment. Contrary to tne practice heretofore employed of removing the cold junctions as far from the heated junction of the thermocouple as possible so as to minimize heat conduction to the cold junctions, the thermocouple as clearly shown in the drawing is composed of a pair of relatively short arms 5| and 52 disposed adjacent the burner and by reason of their short length enabling the entire thermocouple to be disposed within the burner compartment as shown. Whereas, with the cold junction disposed exteriorly of the burner compartment, prompt actuation of the safety device when the flame goes out is not assured because the heat within such compartment may maintain a sufficient temperature differential between the hot and cold junctions for a considerable period of time to prevent prompt actuation of the safety device, the present invention provides that the entire thermocouple is subjected to the heat within the burner compartment, so that the differential in temperature between the hot and cold junctions is that due only to the action of the flame at the hot junction. Hence, immediately that the flame goes out, the differential in temperature that is producing the thermoelectric current ceases to exist and particularly with a construction as here disclosed the gas valve is at once closed, whereby the structure constitutes a true safety device, irrespective of any temperature differential between the interior and exterior of the burner compartment. The use of the metal 53 as an intermediate element between the flame and the hot junction enables the hot junction to be directly responsive to the flame without the relatively expensive metal at the hot junction being in direct contact with the flame. Therefore the life of the thermocouple is extended. Hence the construction herein disclosed assures more prompt actuation of the safety device, provides a longer life for the thermocouple and enables the use of a smaller, less expensive and more compact thermocouple construction than heretofore used. Convectionandradiationas well as conduction along arms 49 and 50 are here relied on for maintaining the proper temperature at the junctions 59 and 55, but any suitable means may be provided for maintaining these junctions properly cooled.

If preferred one of the junctions 56 and 55 may be made closer to the junction 53 than the other, or it may be so constructed that it tends to retain its temperature longer than the junction 53, so that when the pilot flame goes out junction 53 will cool before the last referred to junction, and thereby a reversal of the thermoelectric current will be obtained through the coil of the electromagnet to the end that the latter may be completely demagnetized. Such a construction, however, is ordinarily unnecessary, particularly where means are provided for normally urging the armature away from the end of the electromagnet as here illustrated and described.

Any suitable means may be provided for preventing escape of gas from the interior of the casing [2 along the valve stem 2| in accordance with the broader features of the present invention but this function is preferably performed by the valve member 20. As here shown the end wall 23 has an inwardly extending tubular'boss or projection 56 surrounding the valve stem,'and the valve member has a rearwardly extending portion 51, of a diameter greater than that of the valve stem 2|, for engagement with the end of the tubular boss 56. When the valve is closed,

- against the tension of the spring 21.

as shown in Fig. 2, the end faces of tubular boss 56 and valve portion 51 are spaced by an amount equal to the total movement when opening the valve but somewhat less than the movement required at the sleeve 25 for straightening out the toggle arms 29 and 30 and engaging the armature 36 with pole hand the electromagnet. Hence, when the valve is opened, as hereinafter described, the end faces of the portions 56 and 51 engage each other, and they are preferably machined or otherwise formed so as to provide a contact that will prevent passage of gas therebetween and along the stem 2| through aperture 22. If preferred, however, the extension 51 on the valve member may be of such length as to cooperate with the inner face of end wall 23, or

the tubular boss 56 may be of such length as to cooperate with the rear face of the valve member 20 to effect the same function.

Means are also preferably provided for enclosing the projecting end of the valve stem and its toggle mechanism so that these parts will be protected against injury from accidental impact, and if desired, said enclosure may be locked. As shown, the casing |2 has, either attached thereto or formed as an integral extension of the end wall 23, a generally rectangular skirt 58 which may constitute a support and means for attachment of a generally rectangular housing 59 that may be telescoped over the operating parts, as shown in Figs. 1 and 2, and suitably attached to the support 53, with or without a look as preferred.

In operation, and assuming that the pilot is lighted, the flame at the junction 53 or extension 53' maintains a thermoelectric current through the electromagnet and the armature 36 is held against the poles of the core 39, in the position shown in Fig. 1. This condition is maintained as long as the pilot is lighted, and gas can flow freely through the port l1 to the main burner. If the pilot flame goes out the thermoelectric current through the electromagnet ceases and the valve stem is free to be moved by springs 42, 21 and 31 so as to engage valve member 20 with the valve seat l1 and stop further flow of gas through the latter.

When the valve member 20 is moved to open position, as by pressing the armature 36 or its arm toward the electromagnet, valve stem 2| slides rectilinearly through the aperture 22,.fo1- lowing the motion of sleeve 25, and the toggle arms 29 and 39 are moved from the position shown in Fig. 2 toward the position shown in Fig. 1. Before armature 36 engages the poles of the elecber 20 engages tubular boss 56 and further outward movement of the valve stem is stopped. Further straightening of the toggle arms, to the position shown in Fig. 1 wherein the armature 36 engages the poles of the electromagnet, causes the sleeve 25 to move outwardly on the stem 2|, as permitted by the slot 34 for the pivot 3|, Thereby the end faces of the members 56 and 51 are drawn into tight contact and are placed under considerable tension, so that they constitute an effective valve to prevent leakage of gas along the valve stem 2|. By preference the arms 29 and 30 are in alinement when the armature 36 is against the pole pieces, so that no component of the force of the springs 31 and 21 must be overcome by the pull of the electromagnet on its armature. Spring 42, however, exerts a pressure against toggle arm 30 when thetoggle arms are in alinement and -tromagnet, however, extension 51 on valve memtends to move saidarms ofi dead center when the armature is released.

When the pilot goes out and by reason of the action of the thermocouple an electric current is no longer generated to energize the electromagnet, spring 42 which is under stress tends to move the toggle arms into angular relationship. As soon as the toggle arms are in angular relationship-springs 21 and 31 move sleeve. 25 to decrease the angle until pivot pin 3| strikes the end of slot 34 with something of an impact. Thereafter the springs 31 exert their tension on the valve stem to decrease the angle between said toggle arms and move the valve stem and its valve member inwardly until the valve member engages the valve seat H, the impact of the pin 3| at the end of the slot 34 tending to overcome any tendency of the valve to stick in open position. Said coil springs 31 are preferably so constructed and arranged that there is substantial residual tension in said springs when the valve member 29 has been engaged with its seat ll so that said valve member is firmly pressed against said seat by the tension of said springs 31.

After valve member has been engaged with its seat l1 no gas can flow to the main burner until the valve is manually opened, and even then said valve cannot be retained in open position until the pilot has been lighted and a thermo-electric current generated by the action of the pilot flame on the thermoelectric couple. Hence the danger of gas escaping, with the resultant dangers of explosion, fire, gas poisoning, etc., is effectually prevented, while a further flow of gas can be obtained only by a deliberate manual manipulation of the valve and a continued flow can be obtained only by reestablishment of the thermoelectric current that exists during the normal operation of the pilot. To reopen the valve 20 the housing 59 must also be removed.

The construction described provides sufilcient force between the armature 36 and the end faces of the core 39, to assure that the armature will be held firmly against the poles of the electromagnet during the normal operation of the device and premature or improper operation of the device will not be caused by jars, vibrations, small fluctuations in the magnitude of the electric current, etc.

It will therefore be perceived that a safety device has been provided by the present invention wherein the electromagnet and its armature as well as all of the movable and operating parts except the valve and its stem are positioned exteriorly of the gas passages. As the device may be positioned at any desired relationship with respect to the burner, and may be located as remote from the heat of the burner as desired, the parts thereof may be effectively insulated from the heat generated by the burner, and they may be composed of materials which might be injured if subjected to the zone of heat closely adjacent to the burner.

Furthermore, it will be perceived that all of the parts of the device built in conformity with the present invention are relatively simple in construction, inexpensive to manufacture and easy to assemble. The parts thereof can therefore be standardized for production in large quantities and at small expense by the use of relatively unskilled labor. At the same time the device is certain in operation, and while on the one hand the area of contact between the armature and the electromagnet poles 'is such as to assure against accidental and improper disengagement thereof, and the releasing tendency of the spring 42 is well within the force available for holding the armature against the poles, said spring assures operation of the toggle when the electromagnetic force ceases and thereafter closing movement of the valve is effected by a resilient force which may be materially greater than said electromagnetic force. The fact that the armature and electromagnet poles are removed from the path of the gas assures that corrosion or other action arising from contact with the gas will not cause adhesion or sticking of the parts and therefore interference with the proper and desired operation of the device. The electroinagnet, armature and operating mechanism are thus fully exposed where they are readily accessible for inspection-and operation, and at the same time they may be readily enclosed in a housing against injury. The valve may close against the gas pressure because it is positively moved into closed position and firmly pressed against its seat. At the same time the construction is such as to prevent leakage of gas therefrom if it is desired to avoid the use of packing glands or the like around the valve stem.

While one embodiment of the safety device has been illustrated and described with considerable particularity, it is to be expressly understood that the invention is not to be restricted thereto as the same is capable of receiving a variety of mechanical expressions, some of which will now readily suggest themselves to those skilled in the art, while changes may be made in the details of construction, arrangement, material and proportion of parts, and certain features may be'used without other features, without departing from the spirit of the invention. Furthermore, while the invention has been illustrated and described as employed in conjunction with a pilot flame, it will be apparent that the invention can also be used as a safety device in connection with other sources of heat to prevent the occurrences of dangerous conditions, as will now be apparent to those skilled in the art. Reference is therefore to be had to the claims appended hereto for a definition of the limits of the invention wherein the term cold junction is employed to designate the junction or junctions removed from the normal position of the pilot flame when the pilot is lighted and the term hot junction is employed to designate the junction or junctions disposed adjacent to or at the pilot flame when the pilot is lighted whether one or a plurality of such junctions are used.

This application is a division of our application, Serial No. 699,590, filed November 24, 1933, for improvements in Safety devices for gas burners.

What is claimed is:

1. In a safety device for gas burners, the combination with a gas burner, a chamber within which said burner is disposed, and electro-responsive control mechanism including an operating winding, of a thermocouple having at least two thermojunctions and which is arranged within said chamber so that said junctions are heated substantially equally by the combustion of gas within said chamber, the thermocouple being electrically connected to energize the operating, winding of said control mechanism by means of the thermoelectric currents produced therein, and a pilot burner adapted to normally maintain a flame which heats the hot junction of said thermocouple above the temperature that exists at the cold junction by reason of the ambient temperature within said chamber to maintain a thermoelectric current through said winding, said junctions rapidly attaining substantially the same temperature to discontinue said thermoelectric current when said pilot flame goes out irrespective of the ambient temperature existing outside of said chamber.

2. In a safety device for gas burners, the combination with a gas burner, a chamber within which said burner is disposed, and electro-responsive control mechanism including an operating winding, of a thermocouple having at least two thermojunctions and which is arranged within said chamber so that said junctions are heated substantially equally by the combustion of gas within said chamber, the thermocouple being electrically connected to energize the operating winding of said control mechanism by means of the thermoelectric currents produced therein, and a pilot burner adapted to normally maintain a flame which 'heats the hot" junction of said thermocouple above the temperature that exists at the "coldf junction by reason of the ambient temperature within said chamber to maintain a thermoelectric current through said winding, a flame resistant metal member at the junction of the thermocouple to be heated and in heat conducting relationship therewith for protecting the metal of the thermocouple from the direct action of the pilot flame, said junctions rapidly attaining substantially the same temperature to discontinue said thermoelectric current when said pilot flame goes out irrespective of the ambient temperature existing outside of said chamber.

3. In a safety device for gas burners, the 'combination with a gas burner, a chamber within which said burner is disposed, and electroresponsive control mechanism including an operating winding, of a thermocouple having at least two thermojunctions and which is arranged within said chamber so that said junctions are heated substantially equally by the combustion of gas within said chamber, the thermocouple being electrically connected to energize the operating winding of said control mechanism bymeans of the thermoelectric currents produced therein, and a pilot burner adapted to normally maintain a flame which heats the "hot junction of said thermocouple above the temperature that exists at the cold" junction by reason of the ambient temperature within said chamber to maintain a thermoelectric current through said winding, and a metal member at the junction of the thermocouple which is to be heated and which alone is directly subjected to the pilot flame whereby said junction is adjacent to and heated by but not directly contacted by the pilot flame, said junctions rapidly attaining substantially the same temperature to discontinue said thermoelectric current when said pilot flame goes out irrespective of the ambient temperature existing outside of said chamber.

4. In a safety device for gas burners, the combination with a gas burner, a chamber within which said burner is disposed, and electroresponsive control mechanism including an operating winding, of a thermocouple having at least two thermojunctions and which is arranged within said chamber so that said junctions are heated substantially equally by the combustion of gas within said chamber, the thermocouple being electrically connected to energize the operating winding of said control mechanism by means of thethermoelectric currents produced therein and comprising arms of dissimilar metal of substantially equal length and cross section, and a pilot burner adapted to normally maintain a flame which heats the hot junction of said thermocouple above the temperature that exists at the cold junction by reason of the ambient temperature within said chamber to maintain a thermoelectric current through said winding, said junctions rapidly attaining substantially the same temperature to discontinue said thermoelectric current when said pilot flame goes out irrespective of the ambient temperature existing outside of said chamber.

5. In a safety device for gas burners, the combination with a gas burner, a chamber within which said burner is disposed, and electroresponsive control mechanism including an operating winding, of a theormocouple having at least two thermojunctions and which is arranged within said chamber so that said junctions are heated substantially equally by the combustion of gas within said chamber, the thermocouple being electrically connected to energize the operating winding of said control mechanism by means of the thermoelectric currents produced therein and comprising relatively short arms of flattened cross section, and a pilot burner adapted to normally maintain a flame which heats the hot junction of said thermocouple above the temperature that exists at the cold junction by reason of the ambient temperature within said chamber to maintain a thermoelectric current through said winding, said junctions rapidly' attaining substantially the same temperature to discontinue said thermoelectric current when said pilot flame goes out irrespective of the ambient temperature existing outside of said chamber.

6. In a safety device for gas burners, the combination with a gas burner, a chamber within which said burner is disposed, and electroresponsive control mechanism including an operating winding, of a thermocouple having at least two thermojunctions and which is arranged within said chamber so that said junctions are heated substantially equally by the combustion of gas within said chamber, the thermocouple being electrically connected to energize the operating winding of said control mechanism by means of the thermoelectric currents produced therein, and a pilot burner adapted to normally maintain a flame which heats the "hot junction oi. said thermocouple above the temperature that exists at the cold junction by reason of the ambient temperature within said chamber to maintain a thermoelectric current through said winding, opposite junctions of said thermocouple being subjected to the same temperature of the ambient in said chamber in the absence of the pilot flame whereby the heat differential between said junctions is dependent only on the existence of the pilot flame at the hot"- junction.

PAUL L. BEIZ. SEBASTIAN KARRER. 

